Commit ad29b9fd authored Feb 13, 2020 by Halil Pasic Committed by Greg Kroah-Hartman Mar 18, 2020

virtio-blk: fix hw_queue stopped on arbitrary error



commit f5f6b95c72f7f8bb46eace8c5306c752d0133daa upstream.

Since nobody else is going to restart our hw_queue for us, the
blk_mq_start_stopped_hw_queues() is in virtblk_done() is not sufficient
necessarily sufficient to ensure that the queue will get started again.
In case of global resource outage (-ENOMEM because mapping failure,
because of swiotlb full) our virtqueue may be empty and we can get
stuck with a stopped hw_queue.

Let us not stop the queue on arbitrary errors, but only on -EONSPC which
indicates a full virtqueue, where the hw_queue is guaranteed to get
started by virtblk_done() before when it makes sense to carry on
submitting requests. Let us also remove a stale comment.

Signed-off-by: Halil Pasic <pasic@linux.ibm.com>
Cc: Jens Axboe <axboe@kernel.dk>
Fixes: f7728002 ("virtio_ring: fix return code on DMA mapping fails")
Link: https://lore.kernel.org/r/20200213123728.61216-2-pasic@linux.ibm.com


Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent c656fc43

drivers/block/virtio_blk.c

+5 −3

Original line number	Diff line number	Diff line
		@@ -339,10 +339,12 @@ static blk_status_t virtio_queue_rq(struct blk_mq_hw_ctx *hctx,
		err = virtblk_add_req(vblk->vqs[qid].vq, vbr, vbr->sg, num);
		if (err) {
		virtqueue_kick(vblk->vqs[qid].vq);
		/* Don't stop the queue if -ENOMEM: we may have failed to
		* bounce the buffer due to global resource outage.
		*/
		if (err == -ENOSPC)
		blk_mq_stop_hw_queue(hctx);
		spin_unlock_irqrestore(&vblk->vqs[qid].lock, flags);
		/* Out of mem doesn't actually happen, since we fall back
		* to direct descriptors */
		if (err == -ENOMEM \|\| err == -ENOSPC)
		return BLK_STS_DEV_RESOURCE;
		return BLK_STS_IOERR;